Hi Michael Harper,
Generally there are two ways you can use / implement JBPM:
1. Embedded, Embed it in your application, so you can call all the API directly from application.
2. Use it as service, Deploy it as war file in server like JBOSS AS, the War has to provice API like REST API so that all other application can interact with it.
I believe each implementation has its own advantages and disadvantages.
by the way, I use it as a service because it is shared by multiple application.
Regards,
Thomas Setiabudi